I have GTX680 Mac Edition by EVGA. I installed the latest Nvidia driver from Sierra 10.12.6 as of Apr 18 2019. I swapped and installed Nvidia GTX1080 Founder's Edition. There is no boot screen but I can get into Mac OS since I know what button to press in that hard drive selection screen. However even after getting passed by the boot screen the Sierra login screen still does not appear and it's pitch black. I do the same thing with GTX680 and Sierra login screen will appear just fine (even when I blindfold myself in the boot screen with GTX680). Am I missing something here? (I'm not asking about the boot screen, I'm asking about the Mac OS screen). Thanks.